| Abbreviation | Definition |
|---|---|
| ISRT | Institute of Statistical Research and Training |
| ISS | Institute for Security Studies |
| ISS | Institute for Standardization of Serbia |
| ISS | Institute of security studies |
| ISSE | Institute for a Secure and Sustainable Environment |
| ISSER | Institute of Statistical, Social and Economic Research |
| ISSH | Institute on Systems Science and Health |
| ISSI | Institute for Strategic Studies of Indonesia |
| ISSI | Institute for the Study of Societal Issues |
| ISSI | Institute of Strategic Studies Islamabad |
| ISSI | Intensive Spanish Summer Institute |
| ISSI | Intermountain Suzuki String Institute |
| ISSI | International Science Summer Institute |
| ISSI | International Space Science Institute |
| ISSI | International Student Summer Institute |
| ISSI | International Studies Summer Institute |
| ISSI | International Summer Science Institute |
| ISSM | Institute for the Study of Security Markets |
| ISSP | Institute for Science Society and Policy |
| ISSP | Institute for Student Services Professionals |